Long Island weather forecast: High heat, humidity, possible thunderstorms

Hot and muggy temperatures will continue through Friday across Long Island and New York City, with a chance of thunderstorms Thursday night and Friday evening.

Temperatures in the 90s with high humidity could make it feel up to 100 degrees, the National Weather Service said in its forecast Thursday.

The weather service issued a heat advisory in effect for noon Thursday through 8 p.m. Friday from New Jersey to western Suffolk County to Riverhead.

Isolated thunderstorms Thursday evening and overnight could bring heavy rain totaling 1 to 2 inches, cause flash flooding and bring lightning and wind gusts up to 58 mph, the weather service said. 

Storms are also possible between 4 p.m. and 10 p.m. Friday. 

Long Island MacArthur Airport reached a high of 92 degrees Thursday,  1 degree short of the 1973 record high of 93 degrees, weather service meteorologist David Stark said.

Shortly before 4 p.m. Thursday, the heat index at MacArthur Airport registered 97 degrees.

Given the humidity, weather service meteorologist Bryan Ramsey said Friday's storm will give off "some pretty good rain rates" between 1 and 2 inches per hour; the worst of the storms will take place between 4 p.m. and 8 p.m.

"We are anticipating some possible damaging winds between 58 to 70 miles per hour," Ramsey said, adding that strong storms could cause power outages or down trees.

Long Islanders should expect lightning and hail larger than an inch during the storms. 

"Anyone doing anything outside today or tomorrow, they'll need to keep an eye out for the lightning," Ramsey said Thursday. "Hail can cause damage to cars that aren't protected, like under a carport in a parking garage."

Lows will be generally warm for this time of year, in the 70s.

The Central Islip school district announced classes said it would dismiss early on Thursday due to the heat advisory in effect.

Friday will see a "rinse and repeat" forecast, with heat index values in the triple digits. 

The highest recorded temperature for June 12 was 92 in 2017.

Ramsey encouraged all to stay hydrated and keep cool in air-conditioned spaces.

State authorities on Thursday afternoon issued an air quality health advisory for Thursday and Friday, noting elevated ozone levels brought about by the high heat. 

"Increased heat can lead to the formation of ground-level ozone, a major component of photochemical smog," the Department of Environmental Conservation and National Weather Service said, adding the surface pollutant is different from the upper atmosphere's protective ozone layer.

The agencies noted automotive exhaust and out-of-state emission sources are the prime sources of ground-level ozone "and the most serious air pollution problems" in the Northeast. 

Suffolk County Health Commissioner Dr. Gregson Pigott announced Thursday morning that all residents, especially young children, seniors, those who exercise outdoors and those with preexisting respiratory or heart problems limit strenuous outdoor activity.

"Anyone who experiences eye, nose and throat irritation, shortness of breath or chest pain, is advised to contact their medical provider," he said in a statement.

Long Islanders can visit the Suffolk County website for a complete list of cooling centers.

In Nassau County, Cantiague Park in Hicksville, Mitchel Field Athletic Complex in Uniondale and Wantagh Park in Wantagh will have cooling centers open from 9 a.m. to 4 p.m. on Thursday and Friday. The Nassau County Family Court building at 1200 Old Country Rd. in Westbury will be open as a cooling center 24/7, a post on the county's social media said.

Also on Thursday, the federal National Integrated Drought Information System said drought conditions on Long Island and in New York City had worsened from moderate to severe. The region has been in drought since early April, the agency said. Drought conditions are expected to persist this month, according to the federal Climate Prediction Center.

While the heat advisory is forecast to be over Friday evening, highs will remain in the lower 90s and upper 80s throughout Saturday and Sunday. But due to a cold front, weekend conditions will feel far less humid, Ramsey said.

"Anyone going out this weekend will still need to stay hydrated and still need to wear sunscreen, but as far as the heat, it should be less dangerous," Ramsey said. 

Temperatures will drop slightly by Monday, into the mid- to upper 80s.